The present invention relates generally to a device used to temporarily plug an underground active pipeline. More specifically, the present invention relates to a plug assembly for installation into large diameter active pipelines that stops the flow of fluids therethrough and allows safe entry and servicing of the pipeline.
When the walls of an underground pipeline have been damaged such that the walls are cracked, pitted or spalled or when a joint in the pipeline fails fluids transported by the pipeline may leak out of the pipeline or underground water may leak into the pipeline. In such situations, it is desirable to repair the damaged pipeline wall or joint to prevent further leakage. When repairing such a damaged pipeline, it has been usual to repair a long pipeline as a whole, by inserting a tubular lining material into the pipeline against the wall thereof and hardening the lining material against the inner wall surface of the pipeline.
Methods for repairing a sewer pipe, for example, involve applying lengthy tubular sheet material, which is prepared from a thickened solution of a curable resin in which high-strength fibers are dispersed, onto the inner surface of the pipeline, bring it into intimate contact with the inner surface of the pipeline and heating it to cure the resin in the sheet material. If a long pipeline is only partly damaged, however, it is undesirable from an economic standpoint to line the whole pipeline and it is desirable to repair only its damaged part.
When lining a sewer pipe by a method as described above, the line must be temporarily taken out of service to allow the repair to be made. Further, the pipeline may have openings therein that allow infiltration of significant ground water. Therefore, it is very likely that water may hinder the curing reaction of the resin, or that the cooling action of water may delay the effective heating of the resin and its curing.
In order to take these pipelines out of service, the line needs to be effectively plugged for a period of time. This prevents flow through the pipeline but causes a backup behind the plug. The traditionally available plug for such an application is an inflatable air bag that is placed into the pipeline. However, these prior art inflatable plugs are relatively large when compared to the size of the pipes being plugged, and they are also comprised of relatively inflexible material such that they may be difficult to insert into the pipe. For example, in the case of a horizontal pipe it may be necessary to insert the plug vertically downwardly through a manhole and then turn the plug 90° such that it can be inserted horizontally into a pipe. Due to the large size and relative inflexibility of the prior art inflatable plugs, such manipulation of the plugs may be difficult.
In view of the foregoing, there is a need for a large diameter pipeline plug that allows easy and reliable installation in an active pipeline. There is also a need for a modular, large diameter pipeline plug that can easily be handled to facilitate installation in space restricted environments. There is a further need for a large diameter pipeline plug that includes various access, drain and inspection ports to facilitate the operation of the lining system ongoing within the pipeline while insuring safety for the workers operating within the environment.